1. Field of the Invention
The present invention is an improvement to known forms of speakers, and particularly bass-reflex subwoofers designed for corner loading. The invention integrate a mono amplifier as part of the acoustic structure of the speaker, in order to permit direction amplification of input signals, improved cooling of the amplifier circuit board, and attenuation of standing waves within the enclosure by virtue of the structure of the amplifier board and its placement.
2. Brief Description of the Prior Art
The preferred embodiment represents integration of a mono amplifier with a bass-reflex speaker adapted for corner-loading, as disclosed in PROPHIT (U.S. Pat. No. 4,567,959), which is incorporated herein by reference with respect to the preferred speaker structure.
A bass-reflex subwoofer within a tubular construction, wherein there is corner loading from a tuned chamber and a bass emitting port, has very high efficiency in terms of conversion of electrical power into acoustic power, in the low-bass region. Extreme pressures are created within the tubular main chamber. Even though the efficiency of such speakers permit operation with as little as 6 watts per channel, there commonly is need for amplification of low frequency signals. The present invention integrates an amplifier assembly which as a physical part of the acoustic chamber, for unexpected advantages over separate components.
It is known the prior art, including PHOPHIT and tubular speakers such as the SAS-T62, available from Southern Audio Services, Inc., Baton Rouge, La., that a bass efficiency of 98 dB at 1 watt in typical installations can be achieved. Such prior art speakers, however, have inherent standing waves, at different frequencies. In order to break up standing waves, fiberglass insulation pack or other interior modifications have been used. For example, OGEE, ET AL. (U.S. Pat. No. 4,126,204) illustrates a ducted bass-reflex speaker system, and discusses advantages from using different forms of sound absorbing material. As also discussed by OGEE, ET AL., the frequencies of standing waves in hollow rectangular ducts are related to the dimensions of the ducts, and it is possible to remove certain standing wave frequencies out of the reproducing frequency range by shortening the length, or height of the duct. OGEE also discloses that it is known to use a colinear pipe within a duct, in order to break up the longitudinal fluctuation of standing waves.
It is also known from FREADMAN (U.S. Pat. No. 4,625,328), that an integrated amplifier and speaker system can be constructed, wherein cooling fins are located directly behind a speaker diaphragm, in order to facilitate heat dissipation from those fins. The present invention likewise integrates an amplifier with a speaker system, but transfers heat both by convection from the front surface of a circuit board by exposure to acoustic waves, and by conduction towards external fins, on the rear surface of an aluminum base plate.
Unlike the prior art discussed above, the present invention solves standing wave problems by placing a circuit board within a speaker enclosure, and also thereby solves circuit element heat generation problems by a combination of acoustic energy convection, and conduction to the fins outside of the enclosure.